1. Field of the Invention
The present invention relates to computer networks and to the management of traffic flow within such networks.
2. Related Art
The management and control of distributed computer networks providing information or processing to users present significant difficulties. As more diverse distributed systems are introduced into the network the network management and control tasks increase in complexity. This may be tackled by manual reconfiguration, upgrade or renewal of elements of the network. However, before the problem can be resolved, it is likely that users will have experienced a period of poor performance or other limitations on their activities.
These problems have been alleviated at least to some extent by the introduction of network management systems. These systems have a network monitor that is arranged to monitor the load on elements of the network and to redirect traffic to distribute the traffic in a more optimal manner. An example of such a system is disclosed in PCT patent application number WO 98/35302. In the disclosed system, the network monitor is arranged to monitor the load/performance of the network (or part of the network) and in addition maintains a model of the network that is optimised at regular intervals. If the performance of the model exceeds that of the actual network the system is arranged to change the configuration of the network so that it conforms to the model.
If, for example, the network being monitored is a distributed database, the system may be arranged to move data around the network to the points at which that data is in most demand. If the network is a set of mirror servers (i.e. a group of servers providing identical information or applications to a user) then the system may be arranged to divert traffic from overloaded servers to servers with spare processing capacity.
When traffic is diverted to an alternative destination, return traffic that results may, in some cases, give an indication of the diverted address. Some applications that access data or applications across a network are sensitive to such changes in address and detection of a change may result in an error state and cause the application to discontinue the communication.